Abstract: GABA and its associated benzodiazepine interactions play an important role in basal ganglia function. Distinctive GABA, benzodiazepine and opiate receptor changes occur in response to striatal lesions and in the human neurodegenerative disorder, Huntington's disease (HD). In animal experiments, the in vivo administration of [3H]flunitrazepam labels benzodiazepine receptors and can demonstrate the receptor changes seen after striatal lesions. It should be possible to measure these receptors in vivo in humans using positron-emission tomographic scanning.